1. Field of the Invention
The present invention relates to a head rest unit for use in a vehicle seat, and in particular relates to a head rest unit which is capable of adjusting its inclination in a forward and backward direction with respect to the seat.
2. Description of the Prior Art
In the conventional head rest unit of this type, there has been produced such head rest unit as exemplarily shown in FIG. 1 of the accompanying drawings. According to this prior art, the head rest (1) is selectively rotatable about the point (a) within the range from the position indicated in solid line up to that indicated in the one-dotted line, thus it is possible to incline the head rest at a desired angle within the angle range of .theta..
However, the above-mentioned conventional head rest unit is disadvantageous in that, when the head rest (1) is inclined forwardly toward the head of an occupant (i.e. the distance between the head rest (1) and the head of the occupant is changed from l.sub.1 to l.sub.2), then the contact area (L.sub.1) defined by the contact of the occupant's head with the head rest (1) will be reduced to that indicated by (L.sub.2), resulting in an extremely narrow contact area. Consequently, such structure of the conventional head rest unit does not provide a good support for the occupant's head.